function [PSNR,NC] = myfun_best_alpha(f,w)
    PSNR = [];
    NC = [];

    [U_w,S_w,V_w] = svd(w);
    y = nsctdec(f,[2,4],'pkva','9-7');   % 高斯对应2 2

    t = y;

    S_w1 = S_w(1:32,1:32);
    S_w2 = S_w(33:64,33:64);
    
    [U_f1,S_f1,V_f1] = svd(t{1});
    [U_f2,S_f2,V_f2] = svd(t{3}{5});

    for i = 1:2:20
        alpha = i*0.01;
        temp = S_f1(1:32,1:32) + alpha * S_w1 ;
        S_f1(1:32,1:32) = temp;
        
        temp = S_f2(1:32,1:32) + 0.2 * (S_w2) ;
        S_f2(1:32,1:32) = temp;

        t{1} = U_f1 * S_f1 * V_f1';
        t{3}{5} = U_f2 * S_f2 * V_f2';
        f_watered = nsctrec(t,'pkva','9-7');

        % 水印图像不可见性测试，PSNR
        f1 = double(f);
        f2 = double(f_watered);
        diff_f = f1 - f2;
        diffImageSquared = diff_f .^ 2;
        mse_value = sum(diffImageSquared(:)) / numel(f1);
        if mse_value == 0
            psnr_value = Inf;
        else
            psnr_value = 10 * log10((1^2) / mse_value);
        end
        PSNR = [PSNR,psnr_value];

        % 鲁棒性测试 高斯噪声
        noise = imnoise2('gaussian',512,512,0,0.02);
        f_gauss_noise = (f_watered) + noise;
        figure;imshow(f_gauss_noise,[]);
        NC_gauss_noise = water_extracted(f,f_gauss_noise,w,alpha)

        NC = [NC,NC_gauss_noise];
    end
end